Method of sealingly securing lead-in wires to glass tubes



Feb. 14, 1967 0 GQTQ ET AL 3,304,165

METHOD OF SEALINGLY SECURING LEAD-IN WIRES TO GLASS TUBES Filed Jan. 30, 1963 Fig. Fig. 2

"' /III/I/III 'IIIIIIIIIII/IIlIl/I/I/II/l United States Patent 3,304,165 METHOD OF SEALINGLY SECURING LEAD-IN WIRES T0 GLASS TUBES Elzo Goto, Chigasaki-shi, Narnio Iwata, OdaWara-shi, and Hrdehiro Shinada, Yokohama, Japan, assignors to :IIokyo Shibaura Electric Co., Ltd., a corporation of apan Filed Jan. 30, 1963, Ser. No. 254,942 Claims priority, application Japan, Jan. 31, 1962, 37 2,843 1 Claim. (Cl. 65-54) The present invention relates to an improved method of sealingly securing lead-in wires carrying electrodes to glass tubes or bulbs with no base.

For instance, with relatively small electric lamp bulbs having no base, that portion of the glass bulb in which the outgoing portions of the lead-in wires are sealingly secured, serves for engagement of the lamp bulb with an appropriate socket and is thus required to be shaped and dimensioned with an accuracy high enough to secure such engagement. conventionally, the sealing portion of the lamp bulb is formed in the following manner. The lead- 1n wires having an electrode proviously joined thereto are first mserted into the glass bulb so as to extend outwardly through the open end portion thereof. Then, the bulb end portion is heated to soften it and placed into a shapmg mold, which is opera-ted to mold the bulb end portion into desired shape and dimensions, while sealingly securing the lead-in wires to the glass. In order that, in the molding process, the bulb end portion is finished accurately as desired in dimensions including thickness, width and length, the amount of glass forming the bulb portion to be processed (in other words, the dimensions of the bulb portion including the external diameter and the thickness) must fully accurately be controlled. Meanwhile, it is not easy to obtain a large quantity of glass tube material having such highly accurate dimensions with uniformity. On the other hand, for instance, when it is desired to employ tube material of larger sizes to form glass bulbs having relatively small sealing portions, difficulties are encountered in the molding of the tube end portion, which in this case involves a complicated procedure of constricting the tube end portion to an accurate diameter before it is collapsed or flattened.

According to the present invention, the above difficulties are fully overcome by first collapsing or flattening the tube end portion to a desired thickness and then cuttilpg off the excess glass portion for obtaining a desired s ape.

The present invention will now be described with reference to the accompanying drawing, which illustrates a practical application of the invent-ion to the manufacture of small-sized electric lamp bulb-s.

In the drawing:

FIG. 1 is a view primarily in section, showing a glass tube with a press mold applied thereto;

FIG. 2 is a diagrammatic front elevational view, partly cutaway, of the glass tube shown in FIG. 1 and oriented 90 degrees thereto;

FIG. 3a is a diagrammatic side elevational view, partly in section, of the glass tube as finally shaped; and

FIG. 3b is a front elevational view of the glass tube shown in FIG. 3a.

Referring to the drawing, and particularly to FIG 1, a filament 2 is supported by a pair of lead-in wires 1, which are inserted in a tube or bulb 3 of soft glass so as to extend outwardly through the adjacent open end portion 4 thereof. The tube end portion 4 is then heated to soften and flattened by a press mold 5 to a desired thickness to seal the lead-in wires in place. The shape of the glass tube, before it is press molded, is indicated by the broken lines in this figure. The flattened end portion is then heated to an appropriate glass-softening temperature, for example, a temperature between approximately 800 C. and 900 C. Then, the surplus glass 6 (FIG. 2), of the flattened tube end portion 4 (on opposite sides of the tube axis) are trimmed or cut off by an appropriate cutter jig or mold. These cuts are substantially axially of the tube to remove the portions 6, indicated by the broken lines. Finally, the flattened glass portion remaining integral with the tube body is press molded to a desired shape by use of a shaping mold 7 and then left to cool and solidify to form a desired sealing portion.

As is apparent from the foregoing, the amount of glass in the sealing portion is determined beforehand by flattening the tube end portion and then cut-ing off the excess glass. Because of this, the sealing portion of the glass tube is formed with ease and extreme accuracy to any desired shape and dimensions irrespective of the dimensions of the glass tube material employed. It will be appreciated that the method of the present invention facilitates automatization of the bulb or tube manufacture, and greatly improves the production efficiency and the quality of products.

Having described and shown one practical application of the present invention, it is to be understood that the invention is not to be limited to the details set forth but many changes and modifications may be effected without departing from the scope of the invention as claimed.

What is claimed is:

A method of sealingly securing lead-in wires to a glass tube of a type adapted to have a terminal sealing portion accurately shaped and dimensioned to fit sockets and the like comprising the steps of: inserting an electrode to be supported by integral lead-in wires in the glass tube so that the wires extend outwardly of the glass tube through the open end portion of the glass tube, heating the tube open end portion to a glass softening temperature, flattening the tube open end portion to a flattened end portion of predetermined thickness by use of a press mold to effect simultaneously sealing of the tube completely across the flattened end portion with the lead-in wires sealed therein, heating the flattened end portion to a glass-softening temperature, trimming only the flattened end portion substan tially axially of the tube without cutting into the tube to determine the amount of glass remaining as the trimmed flattened end portion, and then shaping the remaining trimmed flattened end portion into the desired terminal end portion to fit a socket or the like by use of a shaping mold.

References Cited by the Examiner UNITED STATES PATENTS 1,513,756 11/1923 Hancock 65-166 1,882,613 10/1932 Hunciker 65-54 X 2,561,859 '7/1951 Greiner 65-54 2,650,182 8/1953 Green 156-198 2,965,698 12/1960 Gottschalk 65-59 X 3,073,137 1/1963 Fraser 65-59 DONALL H. SYLVESTER, Primary Examiner. S. LEON BASHORE, Examiner.

R. L. LINDSAY, Assistant Examiner. 

